Describing his own security plans for the investiture, Mr Williams had said in 2009 that the day before the ceremony he picked up his firearm – a pistol – at a briefing in a Caernarfon Missionary Hall but received no holster so kept it in his briefcase.

Mr Williams remembers other security issues.

He said Richard Nixon’s daughter was due to fly into Valley on Anglesey for the investiture.

“I showed two CIA men where she would be sitting at Caernarfon Castle. They took everything in,” he said.

On the day of the investiture, Mr Williams remembered: “The Chief Constable said a diesel train will come here and all the royal family will come out to be taken to the Faenol Estate for coffee and to stretch their legs.

“When they came, the Chief Constable took off his bowler hat and said he’s borrowed this field from this lady (the farmer’s wife).

“The Queen said ‘I’d like to meet her’.

“The Chief went to the farmer’s wife, a Mrs Williams, and said ‘Would you like to meet the Queen?’ She said: ‘No. My Prince is Dafydd Iwan.’

“I thought ‘Bloody hell, here we go’.

“I then realised I was there to deal with things like this.”

Years later Mr Williams, of Deganwy, became a Conwy councillor and chaired the now defunct North Wales Police Authority.